Open Question: Is 5 1/2 hours of sleep enough for a 15 year old?

For the past year or so, since I was 14, I have only been giving myself enough time to sleep for about 5 1/2 hrs on weekdays from about 1.30am untill 7.00 when I get up for school. I feel fine and don't seem to be that tired but everwhere seems to tell me I need 8 hrs sleep. Is this true, or should I go by how I feel with my current sleep time?